For convenience purposes, it is well known to provide garage doors which utilize a motor to provide opening and closing movements of the door. Motors may also be coupled with other types of movable barriers such as gates, windows, retractable overhangs and the like. An operator is employed to control the motor and related functions with respect to the door. The operator receives command signals for the purpose of opening and closing the door from a wireless remote, from a wired or wireless wall station or other similar device. It is also known to provide safety devices that are connected to the operator for the purpose of detecting an obstruction so that the operator may then take corrective action with the motor to avoid entrapment of the obstruction.
All known garage door operator systems use only one radio frequency (RF) receiver. This receiver could be an external bolt-on receiver or could be integrated into a motor control board maintained within an operator housing. The RF receiver receives RF data from a remote control (portable transmitter, wall-station transmitter, etc.) to control movement of the garage door; to control the garage door operator light, other various functions or accessories (e.g. external light fixture); or to control appliances associated with a home network. These RF receivers are typically very high frequency (VHF) receivers designed to receive a manufacturer assigned frequency, such as 300.0 MHz, 315.0 MHz, 390.0 MHz, or 433.92 MHz. All of the remote controls for a specific operator transmit at the respective manufacturer assigned frequency.
There are remote controls which can transmit at multiple radio frequencies that can be used with the different manufacturers' assigned frequencies. For example, one transmitter may be provided with three buttons, wherein each button corresponds to a different manufacturer's operator RF receiver. In other words, actuation of one button transmits at 300 MHz, actuation of another button transmits at 315 MHz, and actuation of the third button transmits at 390 MHz. The following patents are exemplary of operator receiver configurations.
U.S. Pat. No. 5,285,478 to Wornell, et al. discloses a communication system in which a transmitter performs modulation upon a number sequence to be transmitted. The modulation scheme includes embedding a sequence of numbers into a waveform such that the sequence is present in the waveform on multiple time scales. The transmitted waveform has a selected number of different frequency bands of successively doubling bandwidths. Each of the frequency bands includes the sequence of numbers, repeated therein at a certain rate. The rate is directly proportional to the bandwidth of the frequency band. The communication system further includes a receiver designed to average the value of the repeated sequence as received by the receiver. This scheme allows for accurate communication over noisy, uncertain, and/or hostile channels in both point to point and broadcast communication applications. However, the scheme does not allow for the operator to receive different frequency signals.
U.S. Pat. No. 5,991,331 to Chennakeshu, et al. discloses a delay spread created in a digital radio signal to reduce the coherence bandwidth and facilitate frequency hopping to reduce the effect of fading losses within an enclosed propagation environment. The delay spread is introduced into the signal in several ways. One technique disclosed employs a transmitter with two separate antennas one of which transmits the digital signal and the other of which transmits the same signal after a phase delay has been introduced into the signal. The carrier frequency of the signals is hopped between at least two frequencies and a receiver processes the resulting signals. In another embodiment, a single transmit antenna is used but the signal is received by two different antennas with the output signal from one of those antennas being phase delayed before combining it with the other prior to processing by the single receiver circuit. Phase delay is also introduced at baseband into the signals to be transmitted by rotating the I and Q components of the waveforms before modulation.
U.S. Pat. No. 6,078,271 to Roddy, et al. discloses a programmable transmitter which includes a receiver for receiving a coded signal at a desired frequency. The code is stored in memory during a learning mode and is then retransmitted sequentially at a plurality of frequencies, including the desired frequency. During this time, the operator observes the device to be operated and indicates to the transmitter when the controlled device performs the desired function, i.e., when the desired frequency is transmitted. At that time, the operator presses a button on the transmitter, and the transmitter stores the most recently transmitted frequency. Still, only a single receiver circuit is employed.
U.S. Pat. No. 6,333,698 to Roddy discloses a trainable transmitter which includes code generation circuitry and a socket for receiving a plug-in module including circuitry for generating an RF signal. By selecting the appropriate plug-in module, the user can expand the frequency transmission range of the transmitter beyond that which may be pre-installed on the transmitter. But only a receiver capable of receiving a single frequency is disclosed.